JP2000124043A - Inverter transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the firing potential of corona and improve dielectric strength of an inverter transformer, by forming a part where the electric field strength is high at a distance from a secondary winding, and making low the electric field strength near the secondary winding. SOLUTION: This inverter transformer is provided with an insulating bobbin 10 having a winding shaft 12, a primary winding 30 and a secondary winding 40. By arranging a plurality of flanges 13 on the side surface of the winding shaft 12, a plurality of winding trenches 14 divided by the flanges 13 are formed. The primary winding 30 is wound around one trench 14a from among the winding trenches 14, and a winding treanch 14b around which wire is not wound is arranged between the primary winding 30 and the secondary winding 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a configuration of an inverter transformer used for a DC / AC inverter for lighting a cold cathode ray tube or the like for back lighting of a liquid crystal display device.

[0002]

FIG. 6 shows a conventional example of an inverter transformer. A primary winding 3 is wound around a cylindrical winding shaft 2a of an insulating bobbin 2 to which a terminal 1 is attached. A secondary winding 4 is mounted on the side. A pair of magnetic cores 5 and 6 have a structure in which the bobbin 2 is sandwiched from above and below with an insulating sheet 7 therebetween to form a closed magnetic circuit.

FIG. 7 is a diagram showing a distribution state of an electric field between two plate-like electrodes 8a and 8b facing in parallel at a distance d. Now, consider the case where the electrode 8a is at 0 volt and a voltage of VG volts is applied to the electrode 8b.
The electric field when only air is present between 8b is V
At G / d, it is linear with uniform strength throughout. On the other hand, when the dielectric 9 is inserted between the electrodes 8a and 8b, it becomes as shown by the solid arrow. The electric field E2 (= V2 / d2) in the dielectric 9 has a gentle slope according to the relative dielectric constant, and the electric field E1 (= V1 / d1) in the air portion.
) And E3 (= V3 / d3) both have a steep slope which is increased by the amount of relaxation at the dielectric 9 portion.

[0004]

The inverter transformer shown in FIG. 6 has a varnish (not shown) between the primary winding 3 and the bobbin 2 and between the secondary winding 4 and the bobbin 2 in order to increase the dielectric strength. Resin is injected. However, the resin does not completely spread between the primary winding 3 or the secondary winding 4 and the bobbin 2, and many voids may be formed due to generated bubbles and the like. Considering that the primary winding 3 is applied to the electrode 8a and the secondary winding 4 is applied to the electrode 8b in FIG. 7, the primary winding 3 is located close to each other and the dielectric of the bobbin 2 is interposed therebetween. The electric field strength in the gap between the coil 3 and the bobbin 2 and between the secondary winding 4 and the bobbin 2 becomes large.
As a result, a corona discharge may occur between the secondary winding 4 and the periphery of the secondary winding 4 at which a high voltage is applied, that is, the core 5, the core 6, the primary winding 3, and the like, which may cause dielectric breakdown. Was.

[0005]

SUMMARY OF THE INVENTION In view of the above, the present invention is to reduce the withstand voltage of an inverter transformer by forming a portion having a strong electric field away from the secondary winding and weakening the electric field near the secondary winding. It is to improve. That is, the present invention provides an insulating bobbin having a base portion on which a terminal is implanted and a cylindrical winding shaft protruding upward from substantially the center of the base portion, and a primary winding wound around the winding shaft. And a secondary winding positioned below the base portion and electromagnetically coupled to the primary winding, wherein a plurality of flanges are provided on a side surface of the winding shaft to form a plurality of winding grooves divided by the flanges. Is formed, a primary winding is wound around one of the winding grooves, and a winding groove in which a wire is not wound is arranged between the primary winding and the secondary winding. The present invention also provides an insulating bobbin having a base portion to which the terminal is attached, a cylindrical winding shaft protruding upward from substantially the center of the base portion, a primary winding, and electromagnetically coupled to the primary winding. In an inverter transformer having a secondary winding, three or more winding grooves divided by the flanges are formed by providing a plurality of flanges on the side surface of the winding shaft,
The primary winding and the secondary winding are wound around different winding grooves, respectively, and a winding groove in which a wire is not wound is arranged between the primary winding and the secondary winding.

[0006]

1 to 3 show an embodiment of an inverter transformer according to the present invention. FIG. 1 is a front sectional view, FIG. 2 is a plan view, and FIG. 3 is a side sectional view. Plastic bobbin 10
The base unit 11 includes a plurality of terminals 21 and terminals 22 and 23 attached to two opposite side surfaces, respectively, and a cylindrical winding shaft 12 protruding upward from the center of the base unit 11.

[0007] Two flanges 13 are provided on the side surface of the winding shaft 12 and
Two winding grooves 14a and 14b divided by 13 are formed.
The primary winding 30 is wound only on the upper winding groove 14a, and the lead wire 31 is connected to the terminal 21 attached to one side surface of the bobbin 10. Although not shown, the primary winding
The feedback oscillation winding is wound around the winding groove 14a together with 30 and the tap of the primary winding 30 is also taken out.
Are connected to each terminal 21.

A secondary winding 40 on the high voltage side is mounted in a recess 15 provided on the lower surface of the base portion 11. Secondary winding 40
Is electromagnetically coupled to the opposed primary winding 30 via the gap in the winding groove 14b where the wire is not wound and the base 11. As is apparent from FIG. 3, the terminals 22 and 23 provided on one side surface of the base portion 11 are terminals 22 for connecting lead wires of the secondary winding 40.
And an external connection terminal 23. That is, the terminal 23
The short terminals 22 are paired one by one, and are integrally connected inside the base portion 11.

Reference numerals 50 and 60 denote cores made of a magnetic material. The pair of magnetic cores 50 and 60 are opposed to each other while sandwiching the bobbin 10 from above and below to form a closed magnetic path. As is apparent from FIG. 3, the upper core 50 has a flat plate portion 51, outer legs 52 integrally formed at both ends thereof, and a cylindrical central leg 53 integrally formed at the center of the flat plate portion 51. With an E-shaped cross section, the central leg 53 is inserted into a hole in the winding shaft 12. On the other hand, the core 60 attached to the lower side of the bobbin 10 is flat.

[0010] A thin sheet 70 made of an insulating material is inserted between the core 50 and the core 60 so that magnetic saturation hardly occurs. The sheet 70 has a through hole 71 slightly larger than the cross section of the central leg 53 of the core 50, and a slit 72 extending from one side surface to the through hole 71. Lead wire of secondary winding 40
41 (FIG. 2) is connected to the terminal 22 from the slit 72 under the sheet 70.

As described above, in the inverter transformer of the present invention, the secondary winding 40 faces the primary winding 30 via the gap in the winding groove 14b where the wire is not wound and the dielectric of the base portion 11. It is the structure which did. The presence of a gap in the winding groove 14b where the wire is not wound exists between the primary winding 30 and the secondary winding 40, so that the intensity of the electric field between the secondary winding 40 and the base portion 11 is reduced. As a result, dielectric breakdown due to corona discharge is extremely unlikely to occur.

FIG. 4 shows a second embodiment of the present invention.
Only the shape of the lower part of the bobbin 10 is different from the inverter transformer of the first embodiment shown in FIGS. That is, the bobbin 10 in this case has a cylindrical partition wall 16 having an inner diameter larger than the diameter of the central leg 53 integrally formed on the lower surface of the base portion 11.

For this reason, the secondary winding 40 mounted in the concave portion 15 on the outer portion of the partition 16 has an inner side surface formed by a dielectric partition 16 and a gap 18 through the center leg of the core. It will face 53. That is, in the case of this structure, since the partition wall 16 and the gap 18 are interposed between the secondary winding 40 and the center leg 53, the electric field around the secondary winding 40 is smaller than in the first embodiment. Since the effect is further reduced, the effect of preventing dielectric breakdown can be further enhanced.

FIG. 5 shows a third embodiment of the present invention.
Three winding grooves 14a, 14b, 14c divided by three flanges 13 are formed, the primary winding 30 is wound around the winding groove 14a, the secondary winding 40 is wound around the winding groove 14c, and the primary winding is formed. Between the wire 30 and the secondary winding 40,
A winding groove 14b in which a wire is not wound is arranged.

[0015]

According to the present invention, since a portion having a strong electric field is formed at a position distant from the secondary winding and the electric field near the secondary winding is weakened, the corona discharge starting voltage increases, There is an effect that the withstand voltage of the inverter transformer can be improved.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing an embodiment of an inverter transformer according to the present invention.

FIG. 2 is a plan view of the transformer.

FIG. 3 is a side sectional view of the transformer.

FIG. 4 is a front sectional view showing another embodiment of the present invention.

FIG. 5 is a front sectional view showing still another embodiment of the present invention.

FIG. 6 is a front sectional view showing a conventional example of an inverter transformer.

FIG. 7 is an explanatory diagram showing a distribution of electric field intensity.

[Explanation of symbols]

 10 bobbin 11 base 12 winding shaft 13 flange 14 winding groove 16 partition 18 air gap 30 primary winding 40 secondary winding 53 center leg

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Minoru Nakano 18th Gomigaya, Tsurugashima-shi, Saitama Toko F-term in Saitama Works (reference) 5E043 AA01 BA01

Claims (3)

[Claims] An insulating bobbin having a base on which a terminal is mounted, and a cylindrical bobbin projecting upward from substantially the center of the base; a primary winding wound around the bobbin; In an inverter transformer having a secondary winding positioned below the base and electromagnetically coupled to the primary winding, a plurality of flanges are formed on the side surface of the winding shaft to form a plurality of winding grooves divided by the flanges. An inverter transformer, wherein a primary winding is wound around one of the winding grooves, and a winding groove for winding no wire is disposed between the primary winding and the secondary winding. 2. A pair of cores made of a magnetic material forming a closed magnetic circuit by being vertically butted with a bobbin interposed therebetween,
A central leg inserted into the hole of the bobbin is provided on at least one of the cores, and a cylindrical partition wall having an inner diameter larger than the diameter of the central leg is formed on the lower surface of the base of the bobbin. Into the hole of the winding shaft and the partition wall,
2. The inverter transformer according to claim 1, wherein an inner side surface of the secondary winding faces the center leg of the core via a partition and a gap. 3. An insulating bobbin having a base to which a terminal is attached, a cylindrical winding shaft protruding upward from substantially the center of the base, a primary winding, and a secondary winding electromagnetically coupled to the primary winding. In an inverter transformer including a secondary winding, three or more winding grooves divided by the flange are formed by providing a plurality of flanges on the side surface of the winding shaft, and the primary winding and the secondary winding are formed by different windings. An inverter transformer, wherein each winding is wound in a groove, and a winding groove in which a wire is not wound is arranged between the primary winding and the secondary winding.